I have a problem with my computer, would appreciate any hints/ideas. It usually begins not immediately after booting Windows, but at some unpredictable point in time, which doesn't seem to correlate with any specific actions of mine. First sign of a problem is process System starting to consume 25% CPU time steadily. I have a quad-core CPU, so it might be one thread working non-stop. At this point micro-freezes start to occur - screen stops refreshing, but if I have, say, music player running - it continues playing. If I try to do something between the freezes, like open Start menu, it will freeze completely and forever. If I press reset button the PC will shut down and then start cold, as opposed to usual reset behavior (which doesn't include PC shutting down).

I have noticed that full restart upon reset is usual for hardware problems, but I think this problem isn't related to at least motherboard-CPU-RAM-videoadapter. It certainly isn't caused by overheating.

One very important not is that it seems to be related to Windows hosted WLAN network: I have USB Wi-Fi dongle and have configured a hosted network to share cable Internet connection with Wi-Fi devices. I am not 100% certain there's a strong connection, but in 9 or 10 cases when I enabled the network (by executing netsh wlan start hostednetwork), it did freeze eventually (sometimes within minutes of starting the network, sometimes within hours), and on at least 10 days when I didn't start the network it never froze, no matter how I used the computer).

There are no critical/error entries in the events log that I can suspect as being related, only regular stuff like "driver not loaded". I have found no critical/error events that are being logged around the time of freeze occurring and are not logged during normal boot without starting the WLAN.